1. Field of the Invention
The present invention relates to a silicon-on-insulator (SOI) substrate, a method for manufacturing the SOI substrate, a semiconductor device using the SOI substrate, and a method for manufacturing the semiconductor device.
2. Description of the Related Art
In recent years, instead of a bulk silicon wafer, integrated circuits using a silicon-on-insulator (SOI) substrate where a thin single crystal semiconductor film is present on an insulating surface have been developed. Since parasitic capacitance between a drain of a transistor and a substrate is reduced using the SOI substrate, the SOI substrate has attracted attention as a substrate which improves performance of semiconductor integrated circuits.
One of known methods for manufacturing an SOI substrate is a Smart Cut (registered trademark) method. An outline of the method for manufacturing an SOI substrate by a Smart Cut (registered trademark) method is described below. First, hydrogen ions are implanted into a silicon wafer by an ion implantation method to form an embrittlement region at a predetermined depth from a surface. Then, the silicon wafer into which the hydrogen ions are implanted is attached to another silicon wafer with a silicon oxide film interposed therebetween. After that, a single crystal silicon layer can be formed on the silicon wafer in such a manner that a heat treatment is performed so that the silicon wafer into which hydrogen ions are implanted is separated as a thin film in the embrittlement region. The Smart Cut (registered trademark) method is also referred to as a hydrogen ion implantation separation method.
A method has also been proposed in which a single crystal silicon layer is formed over a base substrate made of glass by such a Smart Cut (registered trademark) method (for example, see Reference 1). Since glass substrates can have a larger area and are less expensive than silicon wafers, the glass substrates are mainly used for manufacturing liquid crystal display devices and the like. With the use of glass substrates as base substrates, inexpensive large-area SOI substrates can be manufactured.